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This LM317 Calculator can be used to choose the correct resistor values for the LM117-LM317 Voltage regulators.

For an LM317, LM217 or LM117 you can either select your resistor values from the E24 decade list to calculate the LM317 output Voltage, or input your target voltage and value for R1 to get a "ideal" R2 resitor value for the LM317.  This Ideal resistor of course may not exist, but sometimes can be made up from more than one resistor, or alternatively will allow you to estimate the optimum variable resistor value to fine tune your LM317 circuit.

Typical Values for R1 are between 120Ω and 240Ω and you would be well advised to stick to values in this range.

The calculation comes from the Dataseet for the LM117-LM317, although omits the error correction from the calculation.  However as resitors have a tolerance of 1-10% in comparison such a small error correction is probably irrelavent for most builders.

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Eugene  - Thanks |06-04-2009 21:08:03 This is cool. Thanks alot Reply | Quote 0 0

Justblair  - Thanks for the feedback |06-04-2009 21:35:31 Thanks Eugene. I'm glad you found the calculator useful. I plan to add more to the site, so if there is others you would find useful. (or anyone else for that matter) please feel free to ask. JB Reply | Quote 0 0

Steffen |06-08-2009 22:00:10 Hi, Great site and I just did the sure ta2024 mods like you wrote. Huge improvement . I wonder though, could you write basic things like wattage rating on the resistors used for the LM317? Many basic things are not easily understood for beginners (even though your site is very beginner friendly). The same goes for the LPF cap mod for the TA2024. What Vac rating should one choose if one would like to replace the 1uF standard caps with a correct 2,2uF cap? Reply | Quote 0 0

Justblair  - Thanks for the comments |06-08-2009 22:47:27 Hi Steffen Thanks for the comments, glad things have gone well with your amplifier mods. To answer the question of the capacitors. You mention the lpf, but I am thinking you may have meant the signal line cap? No matter, the VAC required is minimal. The voltages on this are at signal line level, about 2V swing. If you are using polypropylene caps as I would suggest, at 2.2uf values you will find the available caps will be in the 100's of Volts ratings. As for the resistor values, sorry I neglected to mention them. You can calculate the wattage ratings required by using Ohms Law I (Current)=Voltage/Resistance The voltage accross the combined values is likely to be something like 12/2000 0.006 (for a 12v output say) To calculate power we take I^2 times the resistance = 0.006 x 0.006 x 2000 = 0.072. You can see that 1/4w values are fine for this application. Reply | Quote 0 0

Steffen |10-08-2009 12:33:46 Yes of course... I meant the signal line cap I bought some film polyprops and the cheapest were the 100v rating ones so I took those. Is the 100v rating DC or AC when it is just written as 100v? "The voltage accross the combined values is likely to be something like 12/2000 0.006 (for a 12v output say)" what is the different values and where do you get them from? The 12 i from 12v? What is 2000 and 0.006 derived from? Reply | Quote 0 0

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